The evolution of nonlinear internal waves from the Luzon Strait, in the South China Sea (SCS) deep basin, on shelf break, near Dong-Sha Island, and in shallow coastal water has been observed by satellite remote sensing, shipboard instruments, and moorings. Internal wave distribution maps have been compiled and updated from more than one hundred satellite images in SCS from 1993 to 2007. Based on these distribution maps, most of the internal waves in the northeastern part of the SCS were propagating westward. The wave crest can be as long as 200 km with large amplitudes of 140 m, due to strong current from the Kuroshio branching out into the SCS through the Luzon Strait. Waverelated processes have also been presented such as wave refraction, generation, depression/elevation waves, upwelling, and mode-two waves. The schematic diagram of internal tides and waves near the Luzon Strait from many SAR images shows potential sources for wave generation. Recently, internal waves on the shelf break in the northwestern part of SCS near Hainan observed by satellite and mooring have been studied. Some results on wave characteristics, oil platform operation, feature tracking with sequential sensors, and environmental monitoring are summarized.
The ocean current over topographic features such as a sill or continental shelf in a stratified flow can produce nonlinear internal waves of tidal frequency and has been studied by many researchers (Liu et al., 1986). Their observations provide insight into the internal wave generation process and explain the role they play in the transfer of energy from tide to ocean mixing. It has been demonstrated that surface signatures of these nonlinear internal waves are observable from satellites (Apel et al., 1985; Liu et al., 1985) in the Synthetic Aperture Radar (SAR) images (Liu and Wu, 2001).